TRAGIC SURVIVOR: Parneeta Sidhu, the pregnant wife of slain Dr. Vajinder Pal Toor, ventures out of the house yesterday with their three-year-old son.. (robert kalfus)

The enraged, unemployed doctor who gunned down a Yale physician allegedly planned to continue his murderous rampage in Brooklyn — armed with 1,000 rounds of ammo, three guns and a hit list that included a city doctor and hospital administrator.

Authorities said Lishan Wang — who is charged with murdering his former supervisor, Dr. Vajinder Pal Toor on the victim’s doorstep Monday — also had plans to exact revenge on two other Kingsbrook Jewish Medical Center colleagues who, like the slain man, were “directly involved” in his firing, authorities said yesterday.

“What truly scares me is he could have gotten into this place and initiated a massacre,” said a doctor at Kingsbrook, where Wang was canned in 2008 as a resident for disappearing while on duty.

As he was brought in shackles into a Connecticut courtroom yesterday and charged in Toor’s murder, former colleagues in Brooklyn described Wang as a ticking time bomb who terrified hospital staff.

“He was mentally unstable,” a doctor said of Wang, who began his internal medicine residency at Kingsbrook in 2006. “Many doctors said he was violent.

“People were afraid to give him orders,” the doctor said. “He was very aggressive with the attendants, screaming and yelling, ‘Why do you interrupt me? Can’t you see I’m busy?’ He had anger problems.

“If he was asked to do something, and he was under stress, he would blow up.”

That held true on the day in 2008 when, in a fit of rage over being reprimanded, he screamed at his superior, Toor, and hurled an ethnic slur at him, leading to him getting the ax.

“[Wang] was sitting in the library studying while a patient was dying in the ICU. The nurses were paging him for four hours,” the doctor said.

“And then Vajinder was called, who was the chief resident,” the doctor said. “Vajinder found him sitting and studying in the library.”

“It was putting him down,” the doctor explained. “It was like, ‘Go back to your country.’ ”

In addition to the information Wang had about the Kingsbrook employees, he was carrying a photo of Toor, as well as Google directions to his Connecticut home, the handguns, a wig, a hammer and a knife stuffed into a bag, cops said.

Wang, 44, had spent at least a day hunting Toor — staking out his Branford home and driving around his block in a van.

“To keep this anger for [two] years and come back to do something like that is truly bad,” said a Kingsbrook doctor. “He had so much hatred for the hospital.

“He could have come here and he could have shot us.”

Branford police, when they found Wang’s apparent hit list, immediately called Kingsbrook’s security chief to do a “welfare check” on the targeted workers. Both were OK. Their identities were not disclosed.

In a pending Brooklyn federal court lawsuit against Kingsbrook, Wang, a Chinese national, specifically mentioned by name Toor and several other doctors he accused of unfairly treating Chinese doctors. He also singled out human-resources vice president John McKeon.

Wang yesterday was ordered held on $2 million bail as disturbing new details emerged about the slaying of Toor, 34.

Wang, a married father of three, last weekend drove from his home in Marietta, Ga., to Connecticut in a 1996 Dodge Caravan minivan.

Kalani Lopa, a neighbor of Toor, spotted Wang driving the van near Toor’s house several times Sunday morning, beginning at about 5:30 a.m. Lopa said that at one point he saw the van parked, with Wang walking toward Toor’s house.

On Monday, Toor’s wife, Parneeta Sidhu — who has a 3-year-old son with him and is pregnant with their second child — kissed the doctor goodbye and closed the front door of their home as he walked toward his car.

Suddenly, Sidhu “heard a loud and rapid noise which sounded like gunshots and ran out of the house,” according to a police report. “She saw her husband laying on the ground in the grass.”

Toor was hit with four shots — one to the head, one in each arm, and one in the back.

“What are you doing to my husband?” Sidhu shrieked at the gunman, who then opened fire on her, according to cops.

A female neighbor saw the killer holding a handgun and wearing what looked like a pink “towel that was draped over his head” before he shot at Sidhu, cops said.

“He was standing there, and he did not look like he was in a hurry,” the woman told police.

Minutes later, a Branford cop spotted the maroon van with tinted windows, and gave chase.

After the van abruptly pulled over, the cop pointed a rifle at the driver, ordering him out.

Wang’s voice “trembled” when he told the cop he was coming from New York.

Cops then found two fully loaded semiautomatic handgun magazines in his jacket pocket.

The van had a temporary tag handwritten with “May-08-10.” May 2008 was the month and year of the incident that led to his firing.

In a back-seat compartment, police found two loaded 9mm pistols, a .22-caliber handgun — as well as up to 700 rounds of .22-caliber ammo and up to 300 9 mm rounds.

Eight shell casings found outside Toor’s home later were found to have been fired by the 9 mm pistols, a prosecutor said.

Noting the personal information about Toor and the other two Kingsbrook employees found in the car, cops said, “All three . . . were directly involved with the termination and expulsion of Lishan Wang from the residency program.”